1. Field of the Invention
The present invention relates to an image forming apparatus, and a control method for the image forming apparatus, for switching a printing method based on a state of a drawing object.
2. Description of the Related Art
As a conventional technology, an image forming apparatus employing an electrophotographic method that outputs an image by transferring a toner image formed on a photosensitive drum onto a recording medium, and pressure-fusing the transferred image with a fixing device to fix the image on the recording medium is known. In such an image forming apparatus, oil and moisture (hereinafter referred to as a “fingerprint trace”) from a person that has adhered to the printing paper can cause fixing defects to occur (because the fingerprint trace hinders the transfer and fixing of the toner image by changing the resistivity of the printing paper). The extent of the fixing defect caused by fingerprint traces changes based on the type and the color of the paper used for printing.
Japanese Patent Application Laid-Open No. 2007-286108 discusses an image forming apparatus that, to improve upon the above-described fixing defect problem, includes a function in which an attached fingerprint trace is evaporated by the heat from a fixing device when a paper sheet is passed through the fixing device before printing, after which the paper sheet is again returned to the conveyance path and printing is executed (hereinafter referred to as a “fingerprint trace removal function”).
In the image forming apparatus discussed in Japanese Patent Application Laid-Open No. 2007-286108, the fingerprint trace removal function can be switched between ON (hereinafter referred to as “fingerprint trace removal mode”) and OFF (hereinafter referred to as “normal mode”) based on user selection. In fingerprint trace removal mode, all of the paper sheets used in printing are passed once through a pair of fixing rollers, and then returned to the conveyance path. Consequently, fingerprint trace removal mode has a slower printing speed than normal mode.
However, in a conventional fingerprint trace removal mode, printing is executed regardless of the type of paper or the printing content of the respective paper sheets, even for paper sheets for which there is no need to execute printing based on fingerprint trace removal mode (e.g., printing when a fingerprint trace adheres only to the edges of the paper sheet and toner will only be fixed in the center of the paper sheet, or printing using a paper sheet on which fixing defects due to fingerprint traces do not easily stand out etc.). Consequently, in the fingerprint trace removal mode discussed in Japanese Patent Application Laid-Open No. 2007-286108, unnecessary delays in the printing speed occur by passing even paper sheets on which fingerprint traces do not easily stand out through a fixing device before printing.